The present invention refers to the improvements made in vulcanizing presses for tires and more specifically to improvements for facilitating and for speeding-up the operations for substituting the vulcanizing molds with which these presses are provided.
As already known, a tire-vulcanizing press comprises a frame provided with a lower support plate usually fixed with respect to the floor, which is provided for allowing a vulcanizing mold of the tires to rest upon, and an upper plate that is mobile with respect to the first plate and provided for keeping the mold shut during the vulcanizing phase and for the shifting with respect to the lower plate, for controlling the opening of the mold itself.
A well-known type of tire vulcanizing mold with which the press can be provided, is a centripetal type of mold with sectors that comprises substantially a lower cheek for being connected to the lower plate, an upper cheek that is axially shiftable with respect to the other cheek and a circumferential crown-of-sectors fixed to the upper cheek and hence axially shiftable along with the same but each of which is radially mobile with respect to the upper cheek when under the action of the force transmitted to it by a coupling made between the inclined surfaces made in the sector and on an annular element that holds the crown-of-sectors. The movement of this type of mold requires, on the upper part of the press, not one but two reciprocally shiftable mobile plates and precisely, an upper plate to which the containing-ring for the sectors is fixed, and an intermediate plate to which the upper cheek is fixed.
As for that matter already known to those skilled in the art, apart from being amply illustrated in detail in existing literature and further below in the present description, owing to the effect of the coupling between the inclined surfaces, the relative axial shifting taking place between the two above-mentioned plates, causes the radial shifting of the sectors with respect to the upper cheek. Hence, the vulcanizing mold is connected to the fixed plate and to the two mobile plates, for the purpose of allowing opening and shutting correctly, during the functioning of the press, while the upper cheek and the annular element mentioned above, are connected respectively to an intermediate mobile plate and to the upper plate of the press. Screws, or similar threaded elements, are usually utilized for realizing this connection, and these latter element are inserted into the holes made in the fixed and in the mobile plates of the press and tightened, in correspondance to the threaded holes of the cheeks and of the annular element of the mold, in accordance with those modes that are already known to technicians.
In the above briefly described type of vulcanizing presses, the operations that are necessary for substituting the mold, result in being long-drawn and tedious, while requiring special care and precaution. In fact, for being able to remove the mold from the press, by raising it from the lower plate upon which it rests, it is first and foremost necessary to disconnect the various mold parts, both from the lower plate itself, as well as from the upper plate. For carrying out these operations, it will first be necessary to dispose the press in its open position, and moreover, to provide appropriate security measures against the press shutting accidently, thus having access from the inside of the mold to the screw-heads that serve for connecting the lower cheek to the lower plate. Then, following this, it will be necessary to dispose the mold in its shut configuration, to remove the screws that connect the upper cheek and annular element to the upper mobile plate and finally, after having once again raised the mobile plates of the press, it will be necessary to grip the mold, with appropriate means, for raising it and drawing it away from the fixed plate.
Moreover, the previously mentioned operations can be effectuated only after the mold has substantially attained a room-temperature i.e. after a period of time that is sufficiently long enough for allowing the various mold and press parts to cool down, after the termination of the normal work-cycles. This period of time, which can take longer time than that necessary for carrying out the operations of dismantling the mold itself from the press, being added to the period of time required following this for returning the press back to the temperature of exercise, involves a considerable reduction in the output of the machines, especially when these machines are destined for producing a limited series of tires. Hence, it is evident that the operations necessary for substituting the mold in the described type of presses, prove to be rather difficult, while requiring particular precautions, and the time that is needed on the whole from the moment of interrupting the manufacturing of tires on the press until such time as the press itself can resume to manufacture a different type of tire results in being considerably lengthly.